Fantastic took me ages searching to find the solution but this worked thanks to : cacb for the post above:
My full C++ code to send 7 characters of user input to the board without resetting it was as follows:
// SensorWebPC.cpp
// Pass the port name in the command line - e.g. sensorwebpc comm2
// Original code from sensorwebpc
// code slightly modified by Z Coldrick 18-Jun-2010
#include "stdio.h"
#include <windows.h>
#include <iostream>
using namespace std;
void PrintError( LPCSTR str)
{
LPVOID lpMessageBuffer;
int error = GetLastError();
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM,
NULL,
error,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), //The user default language
(LPTSTR) &lpMessageBuffer,
0,
NULL
);
printf("%s: (%d) %s\n\n",str,error,lpMessageBuffer);
LocalFree( lpMessageBuffer );
}
int main(int argc, char* argv[])
{
// open port for I/O
HANDLE h = CreateFile("com4",
GENERIC_READ|GENERIC_WRITE,
0,NULL,
OPEN_EXISTING,0,NULL); // my adruino on com4 but this value can be read from argv
if(h == INVALID_HANDLE_VALUE) {
PrintError("E012_Failed to open port");
} else {
// set timeouts
COMMTIMEOUTS cto = { 1, 100, 1000, 0, 0 };
DCB dcb;
if(!SetCommTimeouts(h,&cto))
PrintError("E013_SetCommTimeouts failed");
// set DCB
memset(&dcb,0,sizeof(dcb));
dcb.DCBlength = sizeof(dcb);
dcb.BaudRate = 9600;
dcb.fBinary = 1;
dcb.fDtrControl = DTR_CONTROL_ENABLE;
dcb.fRtsControl = RTS_CONTROL_ENABLE;
dcb.fOutxCtsFlow = 1;
dcb.fRtsControl = DTR_CONTROL_HANDSHAKE;
dcb.fDtrControl = DTR_CONTROL_DISABLE; // avoid reset of arduino board
dcb.Parity = NOPARITY;
dcb.StopBits = ONESTOPBIT;
dcb.ByteSize = 8;
if(!SetCommState(h,&dcb))
PrintError("E014_SetCommState failed");
char buf[8] = "";
cout << "Enter upto 7 characters to send : ";
cin.getline(buf, 8);
DWORD write = 8; // Number of bytes to write to serial port
WriteFile(h,buf,write,&write,NULL); // write is updated with the number of bytes written
DWORD i;
for (i=0; i<write; i++)
{cout << buf[i]; // repeat written chars back in console
}
CloseHandle(h);
}
return 0;
}
This C++ code can be easily compiled with the MinGw/ g++ compiler set to create a stand-alone console app.
(On windows OS)